1. Field of the Invention
The present invention relates to a construction machine, such as a hydraulic excavator, with a front-window opening/closing device for opening and closing a front window of a cabin.
2. Description of the Related Art
As an exemplary front-window opening/closing device of this type, a front-window opening/closing device of a slide type, such as that disclosed in Japanese Unexamined Utility Model Registration Application Publication No. 4-62775, for opening and closing a front opening of a cabin is known.
FIG. 6 illustrates a known front-window opening/closing device of a slide type. This device has an assisting mechanism for assisting the opening and closing of a front window 1. Specifically, one end of a wire 9 is connected to a spring 8 at the rear of a cabin 4 and the other end of the wire 9 is connected to the front window 1, and thus the force of the spring 8 pulls the front window 1 rearward.
However, the front-window opening/closing device with such an assisting mechanism has some problems. For example, since the wire 9 is connected to a lower end of the front window 1 (i.e., connected to a roller shaft 3a of a lower guide roller 3) and the tension of the wire 9 is applied to the lower end of the front window 1, an end of the wire 9 is connected to the lower end of the front window 1 in a manner to extend between a wire guide rail 10 and a roller guide rail 5. This increases frictional resistance between this end of the wire 9 and each guide rail (particularly the roller guide rail 5).
Since, in particular, a front rail 6 has a curved part with a recessed portion 6b at the bottom, frictional resistance in this part increases at an early stage of the opening operation of the front window 1.
Therefore, frictional resistance increased when the front window 1 is opened and closed affects the original assisting function of the assisting mechanism and interferes with smooth operation.
To prevent this problem, an end of the wire 9 may be connected to an upper end of the front window 1. This achieves lower frictional resistance than in the case where it is connected to a lower end of the front window 1. However, in a window-closed state in which the front window 1 is closed, the tension of the wire 9 is directly applied rearward to the upper end of the front window 1. This leads to a reduced pressing force of the front window 1 against the front opening of the cabin 4, and thus degrades sealing performance.